Drill proof plates

ABSTRACT

A drill proof plate formed of a shallow tray having a base and edge walls, with a layer of lumpy, irregular shaped particles of hard cemented metal carbides embedded in a brazing metal, covering the base, but with the free surface of the layer being spaced inwardly of the tray from the plane of the free edges of the wall, with the free surface being irregular and lumpy. The tray is applied against a metal support plate so that the layer free surface is spaced from the surface of the support plate, wherein the tips of drills applied through the support plate against the layer free surface are broken by the layer to prevent penetration thereof.

Unite States Patent 91 Shwayder 1 1 Feb. 13, 1973 1 DRILL PROOF PLATES [75] Inventor: Benjamin H. Shwayder, Franklin,

Mich.

[73] Assignee: Shwayder Chemical & Metallurgy Corporation, Detroit, Mich.

221 Filed: May 18,1971

211 App1.No.:144,429

[52] U.S. Cl ..109/82, 29/1912 [51] Int. Cl ..EQSg 1/02 [58] Field of Search ..109/82, 83, 85; 192/107 M;

[56] References Cited UNITED STATES PATENTS 3,066,402 12/1962 lngels ..29/1912 X 1,977,128 10/1934 Hawkins 2,626,458 1/1953 Lieberman 2,994,762 8/1961 Todd 3,293,029 12/1966 Broderick et a1. ..29/l9l.2 X 3,027,979 4/1962 Pocock ..192/107 M X 3,205 ,841 9/ l 965 Shnayder 109/82 FOREIGN PATENTS OR APPLICATIONS 264,471 3/1928 Great Britain .192/107 M Primary ExaminerAllen B. Curtis Attorney-Cullen, Settle, Sloman & Cantor [57] ABSTRACT A drill proof plate formed of a shallow tray having a base and edge walls, with a layer of lumpy, irregular shaped particles of hard cemented metal carbides em- 4 Claims, 8 Drawing Figures mum. moor PLATES BACKGROUND OF INVENTION The invention herein relates to a drill-proof plate useful to prevent drilling through safe and strongbox walls. Plates of this type are arranged within the wall of the box or safe to be protected to prevent a drill from penetrating into locking mechanisms and other parts to be protected within the box.

An example of this type of plate is illustrated in the patent to Warren M. Shwayder, U. S. Pat. No. 3,205,841 granted Sept. 14, 1965.

The invention herein relates to an improved form of drill proof plates which functions to break the tips of drills applied against the plate.

SUMMARY OF INVENTION The invention herein contemplates forming a drillproof plate out of a shallow, flat tray, having edge walls, with a layer of a drill breaking mixture of particles of hard carbide embedded in a brazing metal arranged upon the base of the tray, with the free surface of the layer spaced inwardly of the plane of the free edges of the tray walls. The tray open face is applied against a support plate, so that the free surface of the layer is spaced inwardly of the support plate wall. The support plate wall may be the wall of a strongbox or a safe door or the like and the plate may be interposed between the safe locking mechanism or other operative part to be protected against drilling.

Thus, although the support plate may be drilled through by a suitable hard tipped drill bit, when the bit passes through the space between the plate surface and the drill breaking layer, the axial acceleration thereof tends to impact the bit tip tending to shatter or break it as it contacts the layer. In addition, the layer being of irregular, lumpy or rough surface, tends to distort or radially move the very tip of the drill bit, causing the tip to wobble under pressure of the layer surface, which wobbling is resisted by the wall of the hole in the support plate through which the drill has penetrated, thus overstressing the bit and causing it to crack or break.

Thus, the improved plate herein, becomes drill proof because it breaks the tips of the drill bits, preventing penetration therethrough.

The plate construction is simple and inexpensive, with the improved results coming from the space formed by depressing the surface of the protective layer within the tray, thus unexpectedly providing an increased resistance to drill penetration by reducing the thickness of the drill proof material.

These and other objects and advantages of this invention will become apparent upon reading the following description, of which the attached drawings form a part.

DESCRIPTION OF DRAWINGS FIG. 1 is a perspective view of the drillproof plate herein.

FIG. 2 is a cross-sectional perspective view of the plate.

FIG. 3 is a cross-sectional view showing the plate assembled against a support wall or support plate.

FIG. 4 is a view similar to FIG. 3, but showing a drill bit penetrating through the support wall.

FIG. 5 is an enlarged fragmentary view of a portion of the support wall, the drill bit and a portion of the protective plate.

FIG. 6 is a view similar to FIG. 5, showing the shattering or breaking of the tip of the drill bit.

FIG. 7 illustrates the drill-proof plate assembled upon the walls of a security box.

FIG. 8 is a cross-sectional view of a plate with a leveling filler applied thereto.

DETAILED DESCRIPTION The drill-proof protective plate 10 is formed of a flat, shallow tray 11, which may be rectangular, as illustrated in FIG. 1, or of some other shape, i.e., round. The tray includes a flat base 12 with bent up edge walls 13. A drill breaking layer 14 is applied within the tray, covering the base from wall to wall.

Such layer is formed of hard, cemented metal carbide particles 15, such as tungsten carbide or one of the other known hard carbides, compacted or packed together and embedded within and generally surrounded by a suitable brazing metal 16, such as conventional copper braze material. The particles are relatively large size, as for example, in the range of 6 to +40 mesh and are irregular in shape.

The free surface 18 of the layer is rough, lumpy, and irregular, and is generally in a plane (see dotted line 19 in FIG. 2) spaced inwardly of the plane (see dotted line 20) of the free edges of the tray walls 13.

Thus, in essence, the plate consists of two components, the shallow tray and the layer which partially fills the tray and whose surface is depressed inwardly relative to the plane of the edges of the tray walls.

In use, the tray is arranged against a support plate or wall 22, which may be the wall of a strongbox or a safe door or the like, and its walls 13 are attached, as by welds 23, to the support plate surface. The free surface of the layer is spaced away from the corresponding surface of the plate 22.

The mechanism to be protected against drilling, as for example, a safe locking mechanism, schematically illustrated by dotted line 24, is arranged upon the base of the drill-proof plate so that the drill-proof plate is interposed between the support plate and the object to be protected against drilling.

In operation, a safecracker attempting to break through the safe or strongbox would normally drill through the support plate 22 and attempt to drill into the locking mechanism 24. A hard carbide covered drill bit 25 will easily penetrate the support plate 22 as illustrated in FIG. 4. However, as the drill bit 25 drills the hole 26, its tip 27 enters into the space between the layer surface 18 and the plate 22 (see FIG. 5) and is momentarily accelerated against the layer surface due to the pressure exerted axially upon the drill. This sudden lunge against the surface of the layer, in many cases is sufficient to shatter the point of the drill and prevent further drilling.

However, in the event that the drill tip has not yet broken, or is partially chipped, it then contacts the rough, irregular carbide particles which tend to shove it sidewise or in a radial direction. However, the body or shank of the drill bit is held by the walls defining the hole 26 against such radial movement so that the relatively stationary drill body coupled with the wobbling drill tip causes substantial strains upon the drill trip which causes the tip to break. The harder the drill tip is pressed against the layer, the more the irregular carbide particles cause the tip to wobble by shoving it sidewise and thus the greater the strain, resulting in effect in a chewing up of the drill tip as illustrated in FIG. 6.

Replacing a chewed up drill bit with a fresh one simply repeats the process. If the drill tip is impacted against the layer, the layer particles tend to move slightly within their soft braze material so that they do not break and are still available to chew up the drill tip.

FIG. 7 shows a typical steel strongbox 30 having a plate 10 secured to each of its side walls and its bottom wall. Likewise, the plates can be applied to the end walls so that the box becomes drill proof and may be used as a separate drill proof box or as a protective box to cover a mechanism to be protected, such as a lock, etc. In such event, a suitable opening can be provided in the box wall and in the covering protective plate to accommodate access to the operating mechanism for normal purposes.

FIG. 8 illustrates a modification wherein the drillproof plate, as described above is provided with a soft filler 32 which fills the space in the tray above the free surface 18 of the layer, to level the open face of the tray. For certain installation purposes this is desirable. The filler may be formed of a soft material such as a plastic or even a soft metal, such as lead which will not interfere with the wobbling of a drill bit causes by contact with the layer, but which will nevertheless function to provide a complete filler so that there is no empty space.

Having fully described an operative embodiment of this invention, we now claim:

1. In a drill proof wall comprising a metal support plate and an inner layer of armor secured to the protected side of said plate, the improvement in which said inner layer of armor comprises a shallow open top metal tray having a base and low upstanding side walls generally perpendicular thereto;

said tray containing a drill breaking layer covering the base of the tray from wall to wall, said layer formed of a solid mass of tightly packed, solid, lumpy irregular shaped particles of hard cemented metal carbide embedded in and surrounded by a brazing metal, with the free surface of the layer being lumpy and irregular due to the particles;

the free surface of said layer generally lying in a plane spaced inwardly toward the base from the plane of the free edges of the tray side walls;

said tray being adapted to be secured to the protected side of said plate with the free edges of its side walls against said plate and with the free surface of said layer parallel to and spaced inwardly from said support plate a distance sufficient to permit axial acceleration of a drill which has penetrated said plate, whereby the hard tip of a drill penetrating the support plate will engage the lumpy, irregular free surface of the layer and tend to wobble within the space between the layer free surface and the support plate surface, while thebody of the drill is held against wobbling within its hole in the support plate, thus inducing strains in the drill tip and causing it to break. 2. A construction as defined in claim 1, and including a soft filler material covering the layer and filling the tray up to the plane defining the free edges'of the tray walls.

3. A drill-proof wall formed of a metal support plate and a shallow tray having a base arranged approximately parallel to and spaced from one of the surfaces of the support wall, the tray having low upstanding side walls generally perpendicular to said base, the free edges of said side walls being secured to said support plate;

a relatively thin drill breaking layer arranged within the tray and covering its base, with the free surface of the layer spaced from said support plate surface to form a gap between the layer and the plate to permit axial acceleration of a drill which has penetrated said plate;

said layer comprising a solidified, tightly packed mixture of lumpy, irregular, relatively large sized particles of cemented hard metal carbides and a brazing metal embedding and generally surrounding the particles, with the free surface of the layer being lumpy and irregular;

whereby the hard tip of a drill penetrating the support plate will engage the lumpy, irregular free surface of the layer and tend to wobble within the gap between the layer free surface and the support plate surface, while the body of the drill is held against wobbling within its hole within the support plate, thus inducing strains in the drill tip and causing it to break.

4. A drill-proof wall as defined in claim 3, and including a soft filler material covering the layer and filling the gap between the layer and the support wall, the material being sufficiently soft to permit wobbling of the tip of the drill contacting the layer surface. 

1. In a drill proof wall comprising a metal support plate and an inner layer of armor secured to the protected side of said plate, the improvement in which said inner layer of armor comprises a shallow open top metal tray having a base and low upstanding side walls generally perpendicular thereto; said tray containing a drill breaking layer covering the base of the tray from wall to wall, said layer formed of a solid mass of tightly packed, solid, lumpy irregular shaped particles of hard cemented metal carbide embedded in and surrounded by a brazing metal, with the free surface of the layer being lumpy and irregular due to the particles; the free surface of said layer generally lying in a plane spaced inwardly toward the base from the plane of the free edges of the tray side walls; said tray being adapted to be secured to the protected side of said plate with the free edges of its side walls against said plate and with the free surface of said layer parallel to and spaced inwardly from said support plate a distance sufficient to permit axial acceleration of a drill which has penetrated said plate, whereby the hard tip of a drill penetrating the support plate will engage the lumpy, irregular free surface of the layer and tend to wobble within the space between the layer free surface and the support plate surface, while the body of the drill is held against wobbling within its hole in the support plate, thus inducing strains in the drill tip and causing it to break.
 2. A construction as defined in claim 1, and including a soft filler material covering the layer and filling the tray up to the plane defining the free edges of the tray walls.
 3. A drill-proof wall formed of a metal support plate and a shallow tray having a base arranged approximately parallel to and spaced from one of the surfaces of the support wall, the tray having low upstanding side walls generally perpendicular to said base, the free edges of said side walls being secured to said support plate; a relatively thin drill breaking layer arranged within the tray and covering its base, with the free surface of the layer spaced from said support plate surface to form a gap between the layer and the plate to permit axial acceleration of a drill which has penetrated said plate; said layer comprising a solidified, tightly packed mixture of lumpy, irregular, relatively large sized particles of cemented hard metal carbides and a brazing metal embedding and generally surrounding the particles, with the free surface of the layer being lumpy and irregulAr; whereby the hard tip of a drill penetrating the support plate will engage the lumpy, irregular free surface of the layer and tend to wobble within the gap between the layer free surface and the support plate surface, while the body of the drill is held against wobbling within its hole within the support plate, thus inducing strains in the drill tip and causing it to break. 